Greases thickened with polyamido acid salts



Unite tates GREASES THHIKENED WITH PULYIDO ACID SALTS No Drawing.Application December 31, 1953 Serial No. 401,696

7 Claims. (Cl. 252-436) This invention pertains to grease compositionshaving improved resistance to oxidation and resistance to emulsificationin water. The grease compositions embodied in this invention arethickened with agents which impart greater resistance to oxidation andemulsification in water than thickening agents which are presently used.

Metal soaps of fatty acids, such as calcium and lithium stearates, areexamples of well-known agents which have been used and which are beingused to thicken lubricating oils to the consistency of a grease. Becausesuch metal soaps are pro-oxidative, that is, they increase thesusceptibility of grease compositions to oxidation, it has beennecessary to incorporate great amounts of oxidation inhibitors in thesegreases.

The grease compositions of this invention are more resistant tooxidation and have greater resistance to emulsification in water thanthose thickened with metal soaps of fatty acids. Furthermore, the greasecompositions described in this invention are more resistant to heat thanfatty acid soap thickened greases; that is, at increased temperatures,the thickening agents of the grease compositions of this invention donot lose their thickening action as rapidly as do the metal soaps offatty acids.

The selection of greases for particular jobs involves more than theselection of a grease because of its general appearance at roomtemperature, its consistency at room temperature, its extreme pressurecharacteristics, its melting point, etc. The selection of greases mustbe accompanied by assurance that the grease will maintain its greasecharacteristics and perform its duties over wide ranges of temperatureand wide variances in pressures at the surfaces being lubricated forlong periods of time.

A detrimental result of the oxidation of grease compositions during theperiod of lubrication is the loss in thickening power of the thickeningagent (e. g., the soap) used in the grease composition. When greaseslubricate the desired surfaces, the greases normally become quite warm.When hot greases become oxidized, they lose their grease structure inthe form of a melt. This melt then flows away from the surfaces beinglubricated, thereby producing lubrication failure. In some greases, themelt, upon continued oxidation, becomes hard and brittle, therebyafiording no lubrication of the surfaces. In some instances, the meltbecomes oxidized to the degree where acids are formed, which acids maycorrode the surfaces which are to be lubricated.

It is a tremendous advantage in lubricating systems which are notreadily accessible to use grease compositions which withstand hightemperatures and the effects of oxidations for long periods of time.Greases which are used to lubricate such parts as found in sealedbearings of electric motors, sealed bearings of compressors, rocker armsof airplane motors, numerous pieces of high speed equipment, such ashigh speed motors, must be resistant to oxidation while performing thespecific task of lubricating, and at the same time have high temperaturestability.

Some degree of satisfaction has been obtained in the preparation ofgreases containing lithium soaps of fatty atent ice acids as thickeningagents; however, such products are usually expensive for many of theuses, and also, lithium soap greases usually have less resistance tooxidation than is required in a number of phases of lubrication.

Numerous other grease thickeners which have been heretofore proposed aredisadvantageous in that they may improve one property of a grease at theexpense of other desirable properties, or are insufficiently effectiveto be commercially satisfactory or are too expensive. For example,certain greases suifer from hardening on aging and/ or deteriorate inthe presence of Water. Still others become gelatinous in bearing tests.

industry has long realized that it would be highly eflicient and highlyacceptable to obtain one grease composition embodying the combinedcharacteristics of high water resistance and good resistance tooxidation. It is extremely advantageous to be able to use one greasecomposition which has these combined characteristics, eliminating theconstant turmoil existing in supplying a great number of greases for allthe numerous specified uses.

By the use of the grease compositions of this invention, it is possibleto eliminate a number of specific greases for the above exemplifieduses. The grease composition of the present invention, having thecombined characteristics of high water resistance and oxidationresistance, has a wide variety of applications, particularly where bothwater and high temperatures are encountered, such as in steel millrollers and transfer table bearings, paper mill roller bearings,automotive wheel bearings under winter and flood conditions, includinguse in amphibious military vehicles, high temperature cannery equipment,exposed control surface bearings for aircraft, etc.

Thus, according to the present invention, it has been found thatoxidation resistant and water resistant greases can be prepared by theuse of the new compounds, metal salts of polyamido acids, as thickeningagents in lubricating oils.

The polyamido acid salts set forth herein as thickening agents of thisinvention are prepared by first reacting an alkylene polyamine with amonobasic acid to form the corresponding fatty acid amide, which is thenreacted with a dibasic acid to form the corresponding polyamido acid.This polyamido acid is then reacted with a metal basic substance to formthe metal salt thereof. These reactions are illustrated by the followingequations.

( Ilia (l? O aR1"C NH""R (N- R)zNH-C' Rl OH M(OH),

a O O H l g H (R1CNHR(N--R) ZNH- Rz-C-O-) M (Polyamido acid salt)wherein R, R and R are straight-chain or branchedchain, saturated orunsaturated, hydrocarbon radicals, R is hydrogen, or the fatty acidradical O H (R1C) or the radical (-ii-Rz-ii-OM) where R represents thesame as noted hereinabove; M is a metal; x is an integer having a valuefrom 1 to 7; and a is an integer having a value equal to the valence ofsaid metal.

For this purpose, it is particularly preferred that R is an ethyleneradical; that R is an aliphatic radical having from 12 to 18 carbonatoms; that R is a hydrocarbon radical having from 2 to 6 carbon atoms;that R is hydrogen; that M is an alkali metal; and that x is an integerhaving a value from 1 to 3.

As used herein, the terms polyamido acid salts and salts of polyamidoacids mean the products represented by polyamido acid salts of Equation3 hereinabove.

The metals which can be used in the formation of the soaps of thisinvention include the metals of Groups I, II, III, and IV of MendeleefsPeriodic Table. Particular metals include lithium, sodium, potassium,silver, magnesium, calcium, zinc, strontium, cadmium, barium, aluminum,and lead. Because of the increased melting points, improved texture andgreater resistance to emulsification in water, it is preferred to usealkali metals, particularly sodium. Greater work stability, coupled withhigher dropping points, are obtained with the sodium soap and the bariumsoap greases.

Examples of the R radicals include the following: methylene, ethylene,and propylene radicals; examples of the R radicals include decyl,decenyl, dodecyl, do- I decenyl, tetradecyl, tetradecenyl, hexadecyl,and octadecyl radicals derived from petroleum hydrocarbons, such asolefin polymers, e. g., polypropylene and polybutylene, etc.

Examples of R radicals include methylene radicals, i. e., (CH M, whereinx is a number from 1 to 8 (2 to 6 preferred). Examples of dibasic acidsfrom which the R radical is obtained include the oxalic acid, malonicacid, methyl malonic acid, succinic acid, methyl succinic acid, adipicacid, pimelic acid, suberic acid, azelaic acid,

sebacic acid, isophthalic acid, terephthalic acid, etc.

Examples of polyamines used in the preparation of the soaps used asthickening agents in grease compositions according to this inventioninclude diethylene triamine, triethylene tetramine, tetraethylenepentamine, pentaethylene hexamine, hexaethyl heptamine, heptaethyleneoctamine, octaethylene nonamine; methylene diamine, dimethylenetriamine; trimethylene tetramine, tetramethylene pentamine,pentamethylene hexamine, octamethylene nonamine; propylene diamine,dipropylene triamine, tripropylene tetramine, tetrapropylene pentamine,octapropylene nonamine, etc.

Lubricating oils which are suitable base oils for the greasecompositions of this invention include a wide variety of lubricatingoils, such as naphthenic base, paraffin base, and mixed base; otherhydrocarbon lubricants, e. g., lubricating oils derived from coalproducts; and synthetic oils, e. g., alkylene, polymers (such aspolymers of propylene, butylene, etc., and mixtures thereof), alkyleneoxide type polymers, dicarboxylic acid esters, liquid esters of acids ofphosphorus, alkylbenzene polymers, polymers of silicon, etc. Syntheticoils of the alkylene oxide type polymers which may be used include thoseexemplified by the alkylene oxide polymers (e. g., propylene oxidepolymers) and derivatives thereof, including alkylene oxide polymersprepared by polymerizing the alkylene oxides, e. g., propylene oxide, inthe presence of water or alcohols, e. g., ethyl alcohol; esters ofethylene oxide type polymers, e. g., acetylated propylene oxide polymersprepared by acetylating propylene oxide polymers containing hydroxylgroups; polyethers prepared from the alkylene glycols, e. g., ethyleneglycol; etc.

The polymeric products prepared from the various alkylene oxides andalkylene glycols may be polyoxyalkylene or polyalkylene-glycolderivatives; that is, the terminal hydroxy group can remain as such, orone or both of the terminal hydroxyl groups can be removed during thepolymerization reaction by esterification or etherification.

Synthetic oils of the dicarboxylic acid ester type include those whichare prepared by esterifying such dicarboxylic acids as adipic acid,azelaic acid, suberic acid, sebacic acid, alkenyl succinic acid, fumaricacid, valeric acid, etc., with alcohols such as butyl alcohol, hexylalcohol, 2-ethylhexyl alcohol, dodecyl alcohol, etc. Examples ofdicarboxylic acid esters synthetic oils include dibutyladipate,dihexyladipate, di-2-ethylhexylsebacate, di-n-hexylfumaric polymer.

Synthetic oils of the alkylbenzene type include those which are preparedby alkylating benzene (e. g., dodecyl benzene, tetradecyl benzene,etc.).

Synthetic oils of the type of polymers of silicon include the liquidesters of silicon and the polysiloxanes. The liquid esters of siliconand the polysiloxanes include those exemplified by tetraethylsilicate,tetraisopropylsilicate, tetra(methyl-Z-butyl)silicate, tetra(4-methyl-2-penta) silicate, tetra( 1-methoxy-2-propyl) silicate, hexyl-4-methyl-2-pentoxy disiloxane, poly (methylsiloxane)poly(methylphenylsiloxane), etc. The above base oils may be usedindividually as such, or in various combinations, Wherever miscible orwherever made so by the use of mutual solvents.

In the preparation of grease compositions of this invention,dicarboxylic acids can be used which are known as dimer acids, which areobtained from Emery Industries, Inc., Cincinnati, Ohio. Thesedicarboxylic acid preparations contain a small amount of tricarboxylicacids (approximately 12%), which also form grease thickening agents Whenreacted according to the present invention.

As previously stated, the thickening agents of this invention wereprepared by reacting monobasic acids with alkylene polyamines to formthe corresponding carboxylic amides, which carboxylic amides were thenreacted with dibasic acids to form the corresponding polyamidocarboxylicacids, which in turn were reacted with metal base substances to form thesalts of the polyamido acids.

More particularly, the thickening agents of this invention were preparedby reacting one mol of a monobasic acid with one mol of an alkylenepolyamine to form the corresponding carboxyamide. One mol of thecarboxyamide was then reacted with one mol of a dibasic acid to form thecorresponding polyamido acid. The resulting polyamido acid was thenreacted with one mol of a metal base to form the desired metal salt ofthe polyamido acid. The following examples illustrate the preparation ofthe thickening agents of this invention.

Example I.Preparati0n of sodium salt grease A mixture of 284 grams (1.0mol) of stearic acid and 206 grams (2 mols) of diethylene triamine washeated with agitation at 390 F. for a period sufficient to allow thetheoretical quantity of water to be removed. To this cooled mixture wasthen added 500 grams (3 mols) of adipic acid, and the mixture was heatedat 390 F. for about 2 hours to remove substantially all of the water ofreaction.

A mixture of 30 grams of the above acid and 170 grams of a Californiasolvent-refined naphthenic base oil having a viscosity of 450 SSU at F.was heated at 460 F. until solution was complete. The mixture wascooled, and 3.7 grams of sodium hydroxide in ml. of water was added. Thewhole mixture was heated to 460 F., then'cooled, and milled through an80 mesh screen. The resulting grease had an ASTM dropping point of 336F. In the boiling water test, the grease was still completely intactafter 60 minutes.

In testing the water resistance property of this grease, a 5 -gram ballof grease was immersed in boiling distilled water. At the end of 60minutes, the grease ball was still intact.

Example II.--Preparati0n of sodium salt grease A mixture of 284 grams (1mol) of stearic acid and 115 grams (1 mol) of diethylene triamine wascharged to a reaction vessel and heated with agitation at 390 F. for aperiod to allow the theoretical quantity of water to be removed from thereaction mixture. To this reaction mixture (cooled) was added 146 grams(1 mol) of adipic acid, and the mixture was heated at 390 F. for abouttwo hours to remove water of reaction. The resulting product was a tan,brittle solid.

A mixture of 30 grams of the above tan polyamido acid and 170 grams of aCalifornia solvent-refined naphthenic base mineral oil having aviscosity of 51 SSU at 210 F. and 450 SSU at 100 F. was placed in areaction vessel and heated, with agitation, at 300 F. until solution wascomplete. The mixture was then cooled to 200 F., after which 1.45 gramsof sodium hydroxide in 10 ml. of water was added. The whole mixture wasthen slowly heated with agitation to a temperature of 500 F. The liquidproduct was poured into a pan to cool. The resulting grease had an ASTMdropping point of 250 F.

Example III.Preparati0n of sodium salt grease A mixture of 284 grams (1mol) of stearic acid and 51.5 grams (0.5 mol) of diethylene triamine washeated at 390 F. until amidation was complete. 73 grams (0.5 mol) ofadipic acid was then added to the mixture and the heating was continuedat about 200 C. for an additional two hours.

30 grams of the above amido acid was added to 170 grams of a Californiasolvent-refined naphthenic base oil and heated at 300 F. until solutionwas complete. After cooling, 2.3 grams of sodium hydroxide in 10 ml. ofwater was added. The mixture was then heated to 500 F., and the productwas poured into pans to cool. The resulting solid gel was milled throughan SO-mesh screen to yield a very smooth homogenous grease. The workedpenetration (ASTM penetration at 77 F. after 60 strokes) was 280, andthe ASTM dropping point was 200 F.

Example lV.Preparati0n of sodium salt grease A mixture of 426 grams (1.5mols) of stearic acid and 94.5 grams (0.5 mol) of tetraethylenepentamine was heated with agitation at 390 F. until substantially all ofthe water of reaction had been removed. To this reaction mixture wasadded 146 grams (1.0 mol) of adipic acid, and the mixture was heated at390 F. for about 2 hours.

A mixture of 30 grams of the above polyamido acid and 170 grams of aCalifornia solvent-refined naphthenic base oil having a viscosity of 450SSU at 100 F. was heated at 300 F. until solution was complete. Themixture was then cooled to 200 F., after which 3.1 grams of sodiumhydroxide in 10 ml. of water was added. The whole mixture was thenheated to 500 F., and the product was cooled. The ASTM dropping pointwas 230 F, and the ASTM penetration at 77 F. after 60 strokes was 315.

The ASTM worked penetration is obtained from the ASTM Test No. D-217,which is described in the Petroleum Division of the ASTM Manual of TestProcedures. In this test, a perforated disk was plunged through a greasesample for the designated number of strokes (e. g.,

6 60 strokes) at 77 F., after which the penetration valu was obtained.

As thickening agents, the polyamido acid salts of this invention may beused in lubricating oils in amounts suficient to thicken the lubricatingoil to the consistency of a grease. For this purpose, from about 5% toabout 50% may be used; however, from about 10% to about 20% are thepreferred amounts for the preparation of grease compositions. In thepreparation of more fluid grease compositions which are useful as airfilter oils, only about 2.5% of the thickening agents of this inventionare necessary for use in lubricating oils. On the other hand, in thepreparation of brick-type greases, approximately 40% of the thickeningagents of this invention will be required. All of the percentages are byWeight.

Besides being excellent thickening agents for greases, the polyamidoacid soaps of this invention are suitable as improving agents inlubricating oils, in pigment manufacture, in dusting powders; forimparting greater waterproofness in such materials as leather, textiles,wood and other fibrous or porous materials; etc.

In addition to the components noted hereinabove, the grease compositionmay include such other additives as various corrosion inhibitors,extreme pressure agents, antiwear agents, stabilizers, V. I. improvers,and the like.

I claim:

1. A grease composition comprising at least 50%, by weight, of a mineraloil of lubricating viscosity, and, in an amount suflicient to thickensaid lubricating oil to the consistency of a grease, a polyamido acidsalt of the formula:

R; o 0 R1 NH-R(N '-R-):NH-ll-Rz-il-O-M wherein R is an alkylene radicalcontaining no more than 3 carbon atoms; R is a hydrocarbon radical ofthe acyl group derived from a fatty acid, said hydrocarbon radicalcontaining from 10 to 22 carbon atoms; R is an alkylene radicalcontaining from 1 to 8 carbon atoms; R is selected from the groupconsisting of hydrogen, fatty acid radicals containing from 10 to 22carbon atoms, and the radical i I (-CRn( -OM) M is an alkali metal; x isa number having a value from 1 to 7.

2. A grease composition comprising at least 50%, by weight, of a minerallubricating oil, and, from 5% to 50%, by weight, of a polyamido acidsalt of the formula:

II I ll ll RiC-NH-R(NR-)=NHCR2-CO--M wherein R is an alkylene radicalcontaining no more than 3 carbon atoms; R is a hydrocarbon radical ofthe acyl group derived from a fatty acid, said hydrocarbon radicalcontaining from 10 to 22 carbon atoms; R is an alkylene radicalcontaining from 1 to 8 carbon atoms; R is selected from the groupconsisting of hydrogen, fatty acid radicals containing from 10 to 22carbon atoms, and the radical O J-Ra OM) M is an alkali metal.

3. A grease composition comprising at least 50%, by weight, of a minerallubricating oil, and, in an amount sufficient to thicken said oil to theconsistency of a grease, a polyamido acid salt of the formula:

wherein R is a divalent ethylene radical; R is hydrocarbon radical ofthe acyl group derived from a fatty acid,

7 said hydrocarbon radical having from 12 to 18 carbon atoms; R is analkylene radical having from 2 to 6 carbon atoms; R is selected from thegroup consisting of hydrogen, fattyacid radicals having from 12 to 18carbon atoms, and the radical n R2('i-oM M is an alkali metal.

4. A grease composition comprising at least 50%, by weight, of a minerallubricating oil, and, in an amount sufiicient to thicken saidlubricating oil to the consistency of a grease, a monovalent metal saltof a polyamido acid of the formula:

a O R1i':NHR(1 IR),NH R,iiM wherein R is an alkylene radical containingno more than 3 carbon atoms; R is a hydrocarbon radical of the acylgroup derived from a fatty acid, said hydrocarbon radical having from 12to 18 carbon atoms; R is an alkylene radical having from 2 to 6 carbonatoms; R is selected from the group consisting of hydrogen, fatty acidradicals having from 12 to 18 carbon atoms, and the radical (i :-R;(i-0M) M is an alkali metal; and x is a number having a value from 1 to3.

5. A grease composition comprising at least 50%, by weight, of a minerallubricating oil, and from to 20%, by weight, of a monovalent metal saltof a polyamido acid of the formula:

Ri-i lNH-(CH:)2(I I-CH OHa),NHiRz-CON wherein R is an aliphatic radicalcontaining from 12 to 18 carbon atoms; R is an alkylene radicalcontaining from 1 to 8 carbon atoms; R is selected from the groupconsisting of hydrogen, fatty acid radicals having from 12 to 18 carbonatoms, and the radical M is an alkali metal; and x is a number having avalue from 1 to 3.

(-iL-Rz-ii-OM) and x is a number having a value from 1 to 3.

7. A grease composition comprising at least by Weight, of a lubricatingoil, and from 10% to 20%, by weight, of a polyamido acid salt of theformula:

wherein R is selected from the group consisting of hydrogen, the radicaland the radical M is a monovalent metal; and x is a number having avalue from 1 to 7.

References Cited in the file of this patent UNITED STATES PATENTS2,239,706 Epstein et al Apr. 29, 1941 2,409,275 Harris Oct. 15, 19462,568,876 White et al Sept. 25, 1951 2,604,449 Bryant et al July 22,1952 2,609,380 Goldstein et al Sept. 2, 1952 2,609,381 Goldstein et alSept. 2, 1952 2,638,449 White et al May 12, 1953 2,638,450 White et a1May 12, 1953 2,752,312 Dixon June 26, 1956 2,756,213 Dixon July 24, 1956Patent No c. 2 849 499 UNITED STATES FATE QEFICE CERTIFICATE or EQTINAugust 26, 1958 Bruce W a Hotten It is hereby certified that errorappeare in the printed specification of the above numbered patentrequiring correetion and that the said Letters Patent should read ascorrected below.

Column 2 Formula (1% for "H M" reed 15 53 I'Formula (3) for H (.3 n.read E i C 0 column 6, line 66, after "metal", and before the period,insert X ie a number having a. value from 1. to '7 5 column 6 lin: 713.,after ":is% second occurrence, insert e 5 column 7, line 9, after"me-tel" before the period, insert 5 x is a number having a Value from 1to 3" column 7 line 35, extreme right-=hanot portion of the formula, for"=ON" read me ilk/1' o Signed and SE1lfii this 6th day of January 1.959a

(SEAL) Attest:

KARL Ho Atteating Oflicer ROBERT C. WATSON Qommissioner of Patents

1. A GREASE COMPOSITION COMPRISING AT LEAST 50%, BY WEIGHT, OF A MINERALOIL OF LUBRICATING VISCOSITY, AND, IN AN AMOUNT SUFFICIENT TO THICKENSAID LUBRICATING OIL TO THE CONSISTENCY OF A GREASE, A POLYAMIDO ACIDSALT OF THE FORMULA: